Hydrophobic sand (or magic sand) is a toy made from

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a soil texture, textur ...

coated with a

hydrophobic In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, ...

compound. The presence of the hydrophobic compound causes the grains of sand to adhere to one another and form

cylinder A cylinder (from ) has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an infi ...

s (to minimize

surface area The surface area of a solid object is a measure of the total area that the surface of the object occupies. The mathematical definition of surface area in the presence of curved surfaces is considerably more involved than the definition of ...

) when exposed to water, and form a pocket of air around the sand. The pocket of air makes magic sand unable to get wet. A variation of this, kinetic sand, has several of the same properties, but acts like wet sand that will not dry out. Hydrophobic sand, whether the wet or dry type, will not mix with water.

History

The earliest reference to waterproof sand is in the 1915 book ''The Boy Mechanic Book 2'' published by ''

Popular Mechanics ''Popular Mechanics'' (sometimes PM or PopMech) is a magazine of popular science and technology, featuring automotive, home, outdoor, electronics, science, do-it-yourself, and technology topics. Military topics, aviation and transportation o ...

''. The Boy Mechanic states waterproof sand was invented by East Indian magicians. The sand was made by mixing heated sand with melted wax. The wax would repel water when the sand was exposed to water. Magic sand was originally developed to trap ocean

oil spill An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially the marine ecosystem, due to human activity, and is a form of pollution. The term is usually given to marine oil spills, where oil is released into ...

s near the shore. This was done by sprinkling magic sand on floating petroleum, which would then mix with the oil and make it heavy enough to sink. Due to the expense of production, however, it is no longer used for this purpose. Hydrophobic sand has also been tested by utility companies in Arctic regions as a foundation for

junction box An electrical junction box (also known as a "jbox") is an enclosure housing electrical connections. Junction boxes protect the electrical connections from the weather, as well as protecting people from accidental electric shocks. Construction ...

es, as it never freezes. It is also used as an aerating medium for potted plants.

Properties

Magic sand

The properties of Magic sand are achieved using ordinary beach sand, which contains tiny particles of pure

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is o ...

, and exposing it to vapors of trimethylsilanol ( CH₃)₃ Si OH, an

organosilicon Organosilicon compounds are organometallic compounds containing carbon–silicon bonds. Organosilicon chemistry is the corresponding science of their preparation and properties. Most organosilicon compounds are similar to the ordinary organic c ...

compound. Upon exposure, the trimethylsilanol compound bonds to the silica particles while forming water. The exteriors of the sand grains are thus coated with

groups. When Magic sand is removed from water, it is completely dry and free-flowing. Aqua Sand, a brand name toy product made using magic sand, can be found in blue, green, or red colors; but all appear silvery in water because of a layer of air that forms around the sand.

Brands

;Kinetic Sand * A toy trademarked and produced by Spin Master Ltd. Kinetic Sand looks like regular wet sand but is available in different colors. It can be molded into any desired shape. It is 98% ultra-fine grain sand mixed with 2% dimethicone (

polydimethylsiloxane Polydimethylsiloxane (PDMS), also known as dimethylpolysiloxane or dimethicone, belongs to a group of polymeric organosilicon compounds that are commonly referred to as silicones. PDMS is the most widely used silicon-based organic polymer, as it ...

), and coated with olive oil. Because of its oil coating, the sand never dries out. It mimics the physical properties of wet sand.Kinetic Sand information
WebPage; Chymist; PDF format. ;Aqua Sand * Similar properties as above.

References

External links

Magic Sand Experiment from the American Chemical Society

Video of how to make Magic Sand
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